It is really called Sar1-GEF. It is in the donor membrane. Sar-1-GDP attaches to Sar-1-GEF and GTP is attached to Sar-1-GDP (now GTP). Sar-1GTP is conformationally changes, a hydrophobic domain exposed, and previous cytosolic protein inserted into donor membrane bilayer.

separates the four SNAREs present in post-fusion complex, using energy from ATP and prepares SNAREs for another round

HIV co-opts SNARE method, how?

virus provides v-and t-snare equivalents. Target membrane does not co-operate. But the target cell does expose CD4/chemokine receptor and the virus binds to that. Virus inserts one snare into membrane, uses the other in typical SNARE formation/fusion.

What is the Golgi's function

to add carbs to proteins and decide twhere to send them

Only proteins that are fully assembled and folded can leave where?

the ER

What binds antibodies when they aren't fully assembled to prevent it from leaving the ER?

BiP

How can the restriction against misfolded proteins leaving the ER be bad?

In cystic fibrosis, a transmbembrane protein Cl- channel is misfolded, but it is still functional. however, it can't leave the ER to get to the plasma membrane.

How do proteins that function in the ER lumen itself get back t the lumen?

Chaperones, an example of this, return by receptor-mediated budding and fusion

-dense vesicles dock at membrane but do not release contents until signal is performed (synapse, Ca2+)

what is pinocytosis?

"cell drinking", which is non-specific and constitutive. capture extracellular fluid via plasma-derived vesicles, in order to promote plasma membrane turnover (they fuse with lysosomes) and internalization of nutrients that lack receptor.

What kind of particles are up for phagocytosis?

large, insoluble particles like bacteria, dead cells, and debris. Only those who can trigger the phagocytic response based on surface chemistry and interaction with receptors on phagocyte. specific.

2. fusion ends when fuses with early endosome, which matures into lysosome, digestion of cargo and some receptors (like LDL) are recycled, some are degraded

opportunistic endocytotic ligands: what does this mean?

for bacteria/toxins/virsuses to gain entry to cells by mimicking other stuff

what are three ways that bacteria/etc can get out/activate of the endosome once endocytosed?

1. use a protein translocator, like in botox toxin. The low pH triggers the heavy chain to act as protein translocator, and translocates light chain into cytosol as toxin, which is a selective protease that targets SNAREs at neuromuscular junction

2. fuse with endosome membrane: induce exocytosis from endosome with pH as a trigger. many membrane encapsulated viruses do this, like HIV

they align when protein from translocation is being translocated into cytosol.

co-translational transport is used for what organelle?

ER

What are multipass proteins?

proteins that have multiple stop-start sequences for transmembrane domains, etc, into ER membrane

Clathrin is a protein coat. where is it used for transport?

to and from trans golgi/endosomes/plasma membrane. also for secretory vesicles

Clathrin is normally _________ in location

cytosolic

COP I/COPII go from ER to and from golgi. how does it work?

Sar-1-GDP, after binding to Sar1GEF (GTPase), gets transformed into Sar-1-GTP and undergoes conformational change via hydrophobic interior spot that was exposed. the domain exposed embeds in membrane and is scaffold for adaptors and other proteins. forms two later coat and deforms membrane to produce a bud

CFTR is what

a chloride channel in ER

what's the difference between exocytotic vesicles and secretory vesicles?

exocytotic comes from the golgi and is constinuous

-secretory vesicles also come from golgi but are regulated from signals

Transport to mitochondria and peroxisome is different how?

there are no transport vesicles, so new lipids from smooth ER taken by phospholipid proteins in hydrophobic pocket

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